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Can spaces that fall outside of the scope of ASHRAE 55-2004, because the physical activity levels result in a time-averaged MET above 2.0 (such as gymnasiums or fitness centers), be excluded from the...

Inquiry

Can spaces that fall outside of the scope of ASHRAE 55-2004, because the physical activity levels result in a time-averaged MET above 2.0 (such as gymnasiums or fitness centers), be excluded from the credit requirements? Also, can spaces that are not normally comfort conditioned (such as warehouse spaces, apparatus bays, vehicle repair facilities, commercial kitchens) be excluded from the credit requirements?

Ruling

**Updated October 1, 2013 to clarify the ruling.
No, spaces with a time-averaged metabolic rate above 2.0 MET must meet the requirements for IEQc7.1 Thermal Comfort—Design/IEQc2.3 Occupant Comfort—Thermal Comfort Monitoring. For these unique spaces, an alternative to the requirements of ASHRAE 55-2004 is acceptable provided the project determines acceptable thermal comfort conditions that meet the intent of the credit, and demonstrates that those conditions will be met. Time-weighted average metabolic rates should be determined based on guidance in ASHRAE 55-2004, Normative Appendix A. Most spaces with MET levels above 2.0 would need to meet the cooling / humidity temperature set points for spaces with MET levels of 2.0 in order to meet the intent of the credit. Exceptions will be considered on a case-by-case basis and must include an explanation that justifies how the intent of the credit is met. Kitchens may pursue this option.

Spaces that are not normally comfort conditioned can only be excluded if they are non-regularly occupied. For regularly occupied spaces that are not normally comfort conditioned, and not able to meet the ASHRAE 55 thermal comfort conditions, the project team must include one or more of the following design alternatives: radiant flooring; circulating fans; passive systems, such as nighttime air, heat venting, or wind flow; localized active cooling (refrigerant or evaporative-based systems) or heating systems; or localized, hard-wired fans that provide air movement for occupants’ comfort.

Inquiry

EQc10 requires compliance with EQc7.1 "Thermal Comfort, Design". ASHRAE 55 uses absolute humidity as the upper moisture limit. EQc10 requires a 60% RH which cuts the ASHRAE 55 absolute humidity in half, or more depending on how cold it gets inside a room when the systems are turned off. If natural ventilation is used at all, and any windows are left partially opened at night, there would be no way to control the humidity to a 60% RH. It is problematic to maintaining a humidity level below 60% when the spaces are unoccupied. The only way to pull humidity out of the space is to run the air conditioning equipment to create condensation, which is itself a potential moisture problem, or to run conditioning systems in heating mode, and so in order to achieve the required humidity levels during unoccupied periods is to potentially run the air conditioning equipment 24 hours a day, seven days a week controlled by a humidistat in the space. There is an apparent flaw in this LEEDS for Schools credit as to comply with this credit the District would need to use up energy and pay higher utility bills during long periods, such as the summer, when the campus is not in use. The USGBC is targeting reducing the carbon footprint of buildings, and the 60% relative humidity requirement is inconsistent with that objective. We suggest some possible alternative mold control techniques during construction of the building instead of conditioning for 60% relative humidity such as: 1. Install mold resistant gypsum board 2. Install weather barrier under exterior finish materials and slab on grade 3. Capillary breaks for footings 4. Provide special inspection for openings and penetrations in the building envelope

Ruling

The project is proposing alternative mold control techniques that would be employed during construction of the building, in lieu of the stated credit requirement of providing HVAC systems and controls designed to limit space relative humidity to 60% or less during all load conditions, both occupied or unoccupied. While the measures cited are commendable and will reduce the likelihood of moisture penetration, they do not however provide sufficient direct impact on the relative humidity levels in the building after construction and during occupancy. As the humidity levels will not be actively controlled during the operation of the building, the potential will remain for mold to grow if humid conditions occur or perpetuate. Applicable Internationally.